The Senate House
The center of law and order in Tertio Rome, the Senate House has always been the most powerful building in the Roman Empire. The Senate House is a large forum that has seating arranged in a circle around a small flat floor. Senators and Citizens and even criminals will "take the floor" to say their piece and those watching in the seats around them will make their judgements based on what they hear.
Senate meetings are open to all citizens of Rome, the Legion and more recently Greeks who have permission from the Legion's Praetors to observe or speak within the Senate. The Senate is a very serious business and they pretty much decide the fate of Tertio Rome and the Legion inside that one room.